A method for manufacturing a super fine line diameter screen printing plate and application thereof

Abstract

The present application relates to a kind of superfine wire diameter screen making method and application.The method is that metal mesh cloth woven with metal wire is used as raw material to make screen, etching liquid is used to etch the metal wire on screen not covered by mask or directly etch all the metal wire of metal mesh cloth, the mask refers to the high molecular film compounded on the surface of metal mesh cloth, the wire diameter is reduced after etching, then the mask is removed, and the plate making of opening pattern is carried out.The technical scheme provided by the present application has the following advantages compared with prior art: the whole surface or the mask according to the demand can be made, the wire diameter of mesh cloth in the required place is made thin, which can be used for the production of finer grid, and the efficiency of solar cell is improved and the consumption of silver paste is reduced;The wire diameter of the pattern area and the non-pattern area can be different, that is, the strength of the mesh cloth is ensured and the required precision is obtained;The difficulty of high-precision mesh cloth production and production cost are reduced.

Description

Technical Field

[0001] This invention belongs to the field of screen printing technology, specifically relating to a method for producing ultra-fine wire diameter screens and its application. Background Technology

[0002] In solar cell manufacturing, conductive silver wires are typically formed using screen printing. A pre-prepared silver paste is placed on a screen, and pressure is applied using a squeegee to force the paste through the openings in the screen pattern onto a silicon wafer placed underneath. The transmitted silver paste reflects the pattern on the screen, forming conductive circuits on the silicon wafer that collect current. In touchpad manufacturing, the same printing principle is used to form touchscreen circuitry on a substrate. The pattern on the screen is achieved through exposure and development.

[0003] The silver lines on the front side of a solar cell consist of two parts: main grid lines and sub-grid lines. The sub-grid lines consist of tens to hundreds of lines, each a few micrometers to tens of micrometers wide, used to collect the photocurrent generated on the silicon wafer surface. The main grid lines consist of two to five lines, each about 0.8 to 2 millimeters wide, used to collect the current from the sub-grid lines and guide it to the circuit being used. However, the presence of the silver lines reduces the effective area of ​​the silicon wafer for receiving light, so the finer the lines, the better.

[0004] The higher the mesh count of the screen, the denser the screen, and the smaller the mesh openings. This allows for a narrower grid width that can be obtained after screen printing, and the wire diameter of the screen must also be reduced accordingly.

[0005] In mesh weaving, the finer the wire diameter, the higher the weaving difficulty and the higher the defect rate. It is very easy to break yarns and have problems such as yarn breakage and twisting during the weaving process. For example, 520 mesh can only be woven 3-4 meters on average in 24 hours. Therefore, the current mesh manufacturing process requires the wire diameter to be above 11μm. Even the finest lines in the mesh still need to be 9-13μm, so the wire diameter needs to be further reduced.

[0006] Chinese patent CN207128384U discloses an ultra-fine wire diameter metal mesh screen, in which the metal mesh is plain-woven from stretched spiral wires. The spiral wires include two double-helical metal wires with a wire diameter ≤8μm. The resulting screen pattern opening width can be less than 50μm, and the width of the printed conductive silver lines is less than 70μm. Although the metal wires used are less than 8μm, the final result, based on the stretching of the double spirals, is that the finest line in the screen is still approximately 14μm. This means there is still no room for further improvement. Therefore, current mesh weaving technology limits the improvement of the precision of screen printing products. Summary of the Invention

[0007] This invention provides a method for manufacturing ultra-fine wire diameter screen printing plates, which solves the current problems with ultra-fine wire diameter screen printing plates with wire diameters below 11μm and their applications.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is: the method for manufacturing ultra-fine wire diameter screens, which includes the following steps: using metal mesh cloth woven from metal wires as raw material to make screens; using an etching solution to etch the metal wires on the screens that are not covered by the mask or to directly etch all the metal wires of the metal mesh cloth; the mask refers to a polymer film covering the surface of the mesh cloth at corresponding positions on the upper and lower surfaces; after etching, the wire diameter is reduced; then the mask is removed to make the screen with the opening pattern.

[0009] Optionally, the diameter of the metal wire used in the metal mesh is above 9μm, preferably 11-20μm, and the mesh count of the metal mesh is 300-800 mesh, preferably 430-520 mesh.

[0010] Optionally, the metal wire is made of stainless steel or tungsten wire, the polymer film is a PI (polyimide) film or a PEEK (polyether ether ketone) film, and the etching solution is an acidic aqueous solution with a pH value of 3-5.

[0011] Optionally, the mask is laminated onto the surface of the mesh fabric by coating, exposing and developing a photosensitive material, or by hot pressing a film with cut-out non-covered areas onto the surface of the mesh fabric.

[0012] Optionally, the thickness of the polymer film is 8-30 μm.

[0013] Optionally, the corrosive liquid includes one or more of sulfuric acid, hydrochloric acid, and nitric acid.

[0014] Alternatively, the target wire diameter can be obtained by controlling the reaction rate of the metal wire in the etching solution.

[0015] Optionally, the concentration of the corrosive solution is 3-20 wt%.

[0016] Optionally, the etching process involves immersing the screen in an etching solution, maintaining a temperature of 20-50°C, allowing it to stand for 6-60 minutes, removing it, rinsing off the etching solution with water, and then drying it.

[0017] Optionally, the drying conditions are: drying at 30-50°C for 5-20 minutes.

[0018] Optionally, the method for creating the opening pattern is photomask creation or laser engraving.

[0019] The present invention also provides a screen printing stencil prepared using the above-described method for producing ultra-fine wire diameter stencils.

[0020] The technical solution provided by this invention has the following advantages compared with the prior art:

[0021] 1. It can be made by masking the entire surface or by making masks as needed, and the wire diameter of the grid in the required area can be made finer, which can be used to make finer grids, thereby improving the efficiency of solar cells and reducing the consumption of silver paste.

[0022] 2. It can make the wire diameter different between the graphic area and the non-graphic area, which ensures the strength of the mesh and achieves the required accuracy.

[0023] 3. It reduces the difficulty and production cost of high-precision mesh fabric manufacturing. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the screen printing plate after the composite polymer mask described in Example 1;

[0025] Figure 2 This is a schematic diagram of the composite polymer mask backing screen described in Example 2.

[0026] As shown in the figure:

[0027] 10 - Screen printing plate; 20 - Metal mesh fabric; 30 - Polymer mask. Detailed Implementation

[0028] For ease of understanding, the following embodiments illustrate the method for manufacturing an ultra-fine wire diameter screen and its application. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation and positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Example 1

[0032] The method for manufacturing the ultra-fine wire diameter screen includes the following steps:

[0033] 1) Mesh Lamination: First, the polyester mesh is stretched and allowed to stand. Then, the polyester mesh yarn is fixed to the mesh frame to form a polyester mesh. Next, hot melt adhesive is used to laminate the metal mesh fabric to the middle area of ​​the polyester mesh to form a composite mesh. Under the action of the top mesh machine, a certain mesh tension is obtained, and the composite mesh is fixed to another mesh frame to obtain a composite mesh. The metal mesh fabric is woven from metal wires with a diameter of 11μm or more. Generally, the wire diameter is less than 20μm. In this embodiment, 11μm wires are used to weave a 520-mesh metal mesh fabric with a mesh thickness of 17μm. The metal wires can be made of stainless steel or tungsten wire. In this embodiment, stainless steel is used.

[0034] 2) Composite Polymer Mask: A polymer mask is laminated onto the upper and lower surfaces of the composite screen fabric. In this embodiment, it is made of PI material. The polymer film covers the areas where the wire diameter does not need to be changed. If the wire diameter is reduced across the entire area, the polymer mask lamination is unnecessary. The lamination method can be to remove the areas that do not need to be covered from the PI film according to the design, and then laminate it onto the screen fabric surface by hot pressing. Alternatively, a polymer mask can be formed in the designed covered area by coating, exposure, and development using photosensitive PI adhesive. In this embodiment, the photosensitive PI adhesive is used for coating, exposure, and development, with a single-sided film thickness of 5μm and a total thickness of 10μm on both sides. The mask formed in this embodiment is as follows: Figure 1 As shown, the grayscale area on the metal mesh 20 of the screen printing plate 10 is the mask 30 formed;

[0035] 3) Adjusting wire diameter: The target plan is to reduce the wire diameter of the metal mesh in the uncovered areas to 9μm. The specific process is as follows:

[0036] The screen with the polymer mask was immersed in an etching solution, which was a hydrochloric acid solution with a concentration of 8wt% HCl (approximately 2.28 mol / L). The solution was kept at 30°C for 50 minutes. After removal, the screen was rinsed with water to remove the etching solution and dried at 50°C for 15 minutes. After etching, the wire diameter was measured using a high-precision three-dimensional measuring instrument, and the yarn thickness was measured using a film thickness gauge. In this example, the etched area yielded a screen with a wire diameter of 9 μm and a thickness of 14 μm. The surface polymer mask was then removed.

[0037] 4) Plate making: The plate making process for the opening pattern is performed. Existing plate making methods are applicable, such as photomask plate making or laser plate making. This embodiment uses laser plate making, specifically including the following steps:

[0038] Lamination: Select PI film and laminate the film layer onto the P surface of the mesh through high temperature lamination to form a polymer layer on the composite mesh;

[0039] Laser engraving: The drawing is pre-aligned to the etched area using mark points. After setting the laser parameters, line width parameters, and size parameters, the laser engraving operation is performed to form the required opening pattern on the film layer in the etched area.

[0040] The resulting screen pattern has an opening width of less than 10μm, and the width of the conductive silver line after printing is less than 18μm. There are no broken grids in the printing and no false printing on the surface. In this example, the wire tension reaches 12N.

[0041] Example 2

[0042] The difference from Example 1 is:

[0043] The metal mesh fabric mentioned in step 1) is a 430-mesh mesh fabric woven from metal wires with a diameter of 13μm; the metal wires are made of tungsten steel.

[0044] Step 2) involves cutting away the PI film from the areas that don't need to be covered (the metal corrosion areas). The film thickness is 6 μm. In this embodiment, it is laminated to the upper and lower surfaces of the screen using a hot-pressing method. The mask formed in this embodiment is as follows: Figure 2 As shown, the grayscale area on the metal mesh 20 of the screen printing plate 10 is the mask 30 formed;

[0045] The target plan described in step 3) is to reduce the wire diameter of the uncovered area to 10 μm. The specific process is as follows:

[0046] The screen with the composite polymer mask was immersed in an etching solution with a concentration of 10wt% HCl (approximately 2.87mol / L), and allowed to stand at 30℃ for 60 minutes. After removal, the etching solution was washed off with water, and the screen was dried at 50℃ for 15 minutes. After etching, the wire diameter was measured using a high-precision 3D measuring machine. In this example, the etched area will yield a 10.5µm wire diameter mesh. The surface polymer mask was then removed.

[0047] Step 4) employs the photosensitive emulsion plate-making method, which specifically includes the following steps:

[0048] Plate making: The plate making of the opening pattern is carried out. All existing plate making methods are applicable, such as photomask plate making or laser plate making. This embodiment adopts the photomask plate making method, which specifically includes the following steps:

[0049] Coating: Select a photosensitive emulsion and apply it to the composite mesh on the P side by scraping. Place it in an oven to dry, forming an emulsion layer on the composite mesh.

[0050] Exposure and development: The coated and dried composite screen is exposed. A 30μm linewidth film is attached to the corresponding position of the composite mesh on the P side. The exposure energy and time are set for exposure. After exposure, the composite screen is developed and dried to complete the exposure process and form an open pattern.

[0051] The resulting screen pattern has an opening width of less than 22μm, and the width of the conductive silver lines after printing is less than 30μm. There are no broken grids in the printing and no false printing on the surface. In this example, the wire tension can reach 12N.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of making a halftone screen with ultrafine lines, characterized in that, The method comprises the following steps: using metal wire woven metal mesh cloth as raw material to make a screen, using an etching solution to etch the metal wire on the screen which is not covered by a mask, the mask is a polymer film covering the corresponding positions of the upper and lower surfaces of the metal mesh cloth, the wire diameter is reduced after etching, then the mask is removed, and the plate making of the opening pattern is performed.

2. The method according to claim 1, wherein The wire diameter of the metal wire used in the metal mesh cloth is greater than or equal to 9 microns, and the mesh number of the metal mesh cloth is 300-800.

3. The method according to claim 2, wherein The wire diameter of the metal wire used in the metal mesh cloth is 11-20 microns, and the mesh number of the metal mesh cloth is 430-520.

4. The method according to claim 1, wherein The material of the metal wire is stainless steel wire or tungsten wire, the polymer film is PI film or PEEK film, and the etching solution is acidic aqueous solution with a pH value of 3-5.

5. The method according to claim 1, wherein The etching solution contains one or more of sulfuric acid, hydrochloric acid and nitric acid.

6. The method according to claim 5, wherein The concentration of the etching solution is 3-20 wt%.

7. The method according to claim 1, wherein The target wire diameter is obtained by controlling the reaction rate of the metal wire in the etching solution.

8. The method according to claim 1, wherein The etching process is to immerse the screen in the etching solution, control the temperature at 20-50 DEG C and stand for 6-60 minutes, then wash away the etching solution with water and dry.

9. The method according to claim 8, wherein The drying condition is to dry for 5-20 minutes at 30-50 DEG C.

10. The method according to claim 1, wherein The plate making method of the opening pattern is photomask plate making or laser plate making.

11. A screen for screen printing, characterized by The screen printing screen is prepared by the screen plate making method of any one of claims 1-10.

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